Gaige, in Chess Tournament Crosstables, has 'Jacobsohn' at Cologne 1911, but 'Jacobson, E.' or 'Jacobsen, E.' at later events in Scandinavia. Di Felice identifies all of these as 'Jacobson, Ernst'. Gaige, in Chess Peronalia has 'Jacobsen, Ernst'. Without further proof, I will assume that the German player was different.